Fluid rotor angular rate sensor and three-axis angular rate sensor utilizing the smae

ABSTRACT

Fluid rotor angular rate sensor with a single sensitive axis having means forming a substantially continuous passageway and having a fluid mass in the passage serving as a fluid rotor. A paddle member is disposed in the passageway and inhibits movement of the fluid rotor in the passage. Means is for provided for sensing the position of the paddle member in the passageway. Electrical means is connected to the means for sensing the position of the paddle member and for applying a restoring force directly to the paddle member which is proportional to the force necessary to accelerate the fluid rotor as the rate sensor is accelerated about the single sensitive axis. The electrical means produces a signal proportional to the angular acceleration and includes means for integrating the signal to provide an output proportional to the rate of turn of the rate sensor about the single sensitive axis. In the three-axis angular rate sensor, three of the single axis angular rate sensors are mounted on X, Y and Z axes.

United States Patent- Sage et al.

[541 FLUID RoToR ANGULAR RATE I SENSOR AND THREE-AXIS ANGULAR RATESENSOR UTILIZING THE SMAE [451 Aug. 8, 1972 3,520,196 7/1970 Morris eta]. ..73/516 Primary Examiner-Charles A. Ruehl AssistantExaminer-Herbert Goldstein [721 I Invent gm? m AttomeyFlehr, Hohbach,Test, Albritton and Her- Km, Calif. [73] Assignee: Systron-IionnerCorporation, Con-' ABSTRACT cord Cahf' Fluid rotor angular rate sensorwith a single sensitive [22] Fil d; M 7, 19 9 axis having mean?l forminga: sgbstantiallyucontinuous passageway an I avmg a in mass m e passage[21] Appl- 822,369 serving as a fluid rotor. A paddle member is disposedv in the passageway and inhibits movement of the fluid [52] US. Cl..73/503 in the P Means is for P for [5 1] Int. Cl. ..G0lp 3/44, GOlp7/00 the Position of the Paddle member in the passageway-- 58 Field ofSearch ..73/505 516 s 17 503 Electrical means is connected to the means.for sensing the position of the paddle member and for applying a 56]References Cited restoring force directly to the paddle member which isproportional to the force necessary to accelerate the UNITED STATESPATENTS flux; rotor as the ratenslensilar is aglcelerated about the sine sensitive axis. e e ectric means produces a g g signal proportional tothe angular acceleration and in- 3074279 l 1963 f cludes means forintegrating the signal to provide an 3 l ,5 output proportional to therate of turn of the rate sen- 3,1 1,565 2/1964 Amzre 73/512 about thesingle sensitive axis In the threeaxis am 3,176,518 M01118 6t ratesansor, three f the single angular rate sensors are mounted on X, Y andZ axes. 3:529:240 9/1970 5 Claims, 10 Drawing Figures M AS ANALOGINTEGRATOR I E0 R1 R2 vv vvvr A I ACCELERATION 2 R, ELECTRONICS t E I ra T 77 l o PATENTED M19 8 I972 SHEET 1 OF 4 F i g. 6

ANALOG INTEG(RATOR Iforneys SENSING A SSEMBLY ELECTRONICS ACCELERATION Il I -l2 dh/o :f

i-Sdb/acl 0 an E INVENTOR. Brqdley 8. Sage 121/22 w f2 l INPUT FREOUNCYIN HZ PATENTED B 9 I972 sum 2 or 4 INVENTOR. Bradley 8 Sage Heino KaseArmrneys PATENTED 8 I972 3.682.003

sum 3 or 4 F i g. 9 INVENTOR. Bradley 8. Sage Y Heino Kase-- AttorneysPATENTEDAus' 8 I972 SHEET [If 4 INVENTOR. Bradley 8. Sagg i0 Kase ,W 3Attorneys FLUID ROTOR ANGULAR RATE SENSOR AND THREE-AXIS ANGULAR RATESENSOR UTILIZING THE SMAE BACKGROUND OF THE INVENTION Angularaccelerometers have heretofore been provided. However, such angularaccelerometers have been relatively expensive. Because of this reason,there SUMMARY OF THE INVENTION AND OBJECTS The fluid rotor angular ratesensor with a single sensitive axis consists of a base plate on whichmeans is mounted which forms a substantially continuous passageway whichserves as a fluid rotor. A paddle member is pivotally mounted upon thebase plate and is disposed in the passageway and is adapted to constrainthe flow of fluid in the passageway. Means is provided for sensing theposition of the paddle member in the passageway. Electrical means isconnected to the means for sensing the position of the paddle member andfor applying a restoring force directly to the paddle member which isproportional the force which is necessary to accelerate the fluid rotoras the base plate is accelerated about the single sensitive axis. Theelectrical means produces a signal proportional to the angularacceleration and includes means for integrating the signal to provide anoutput proportional to the rate of turn of r the base plate about thesingle sensitive axis. In the three-axis angular rate sensor, three ofthe single sensitive axis rate sensors are mounted on X, Y and Z axes.

In general, it is an object of the present invention to provide a fluidrotor angular rate sensor which can be manufactured economically.

Another object of the invention is to provide a rate sensor of the abovecharacter which has very high reliability and which does not suffer fromlife limitations and wear out.

Another object of the invention is to provide a rate sensor of the abovecharacter which only requires a dc. power input and which provides adirect dc. voltage output which is proportional to the angularacceleration or which, with processing, the angular rate.

Another object of the invention is to provide a rate sensor of the abovecharacter which can be incorporated into a three-axis angular ratesensor to take the place of a rate gyro.

Additional object and features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a fluidrotor angular rate sensor incorporating the present invention.

FIG. 2 is an end elevational view of the rate sensor shown in FIG. 1.

FIG. 3 is a side elevational view of the rate sensor shown in FIG. 1. 7

FIG. 4 is a top plan view of the rate sensor shown in FIG. 1 withcertain parts in cross-section.

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 4.

FIG. 6 is an operational block diagram of the rate sensor shown in FIG.1.

FIG. 7 is a graph showing the frequency of response of the rate sensorshown in FIG. 1.

FIG. 8 is a cross-sectional view showing another embodiment of a fluidrotor angular rate sensor incorporating the present invention.

FIG. 9 is an enlarged cross-sectional view of a portion of the ratesensor shown in FIG. 8.

FIG. 10 is an isometric view of a three-axis angular rate sensorutilizing the single axis fluid rotor angular rate sensors of the typeshown in FIGS. 1-5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluid rotor angular ratesensor 10 consists of a generally U-shaped base plate 11 which isprovided with two spaced generally parallel up-turned end portions 11aand 11b in which the end portion 11b has a height which is substantiallygreater than the height of end portion 11a. The rate sensor alsoconsists of a sensing assembly 12 which is mounted upon the base plate11 and which includes, as a part thereof, a tubular assembly 13 which ismounted in the sensing assembly and on the base plate 11. A bellows orexpansion chamber 14 is mounted on the sensing assembly 12 and is alsomounted upon the up-turned end portion 110. An electronics module 16 isalso mounted upon the base plate 1 l.

The sensing assembly 12 consists of a case 17 which is formed of agenerally cylindrical base 18 and a generally cylindrical cover 19. Thebase 18 is secured to an upstanding portion 11b of the base 11 by ascrew 20 (see FIG. 4). The tubular assembly 13 consists of twosubstantially U-shaped sections of tube 21 and 22. The section 22 issecured to the up-turned end portion 11a of the base 11 by suitablemeans such as welding and has one end extending through the cover 19 andhas the other end extending into a coupling 23. The other section 22 hasone end extending through the base 18 and has the other end extendingthrough a hole 24 provided in the upturned portion 11b and is alsomounted in the coupling 23. As can be seen, the two sections 21 and 22generally facing each other so as to provide a substantially continuousor endless passageway 26. A small space 27 is provided between twoadjacent ends of the sections 21 and 22 which is in communication with aspace 28 provided within the cover 19. The passageway 26 and the space28 within the cover 19 are filled with a suitable fluid such as asilicone oil. This silicone oil within the passageway 26 serves toprovide an inertial fluid mass which also can be termed a fluid rotorwhich will have a tendency to remain stationary as the base plate 11 issubjected to angular acceleration about the single sensitive axis forthe sensor.

Means is provided for sensing the force which is necessary to acceleratethe fluid rotor as the base plate 11 is accelerated. This means consistsof a paddle assembly 31 which is provided with a pair of spacedsubstantially planar end paddle members 32 and 33 which are mounted uponand generally extend upwardly from an elongate support member 34 as canbe seen particularly in FIG. 5. The end paddle member 33 is disposedwithin the space 27 and is of a size which is substantially greater thanthe cross-sectional area of the passageway 26 to thereby impede orconstrict the flow of the fluid through the passageway 26. As will benoted, the space 27 is slightly wider than the thickness of the paddlemember 33 so as to permit some movement of the paddle member 33 in adirection parallel to the flow of fluid through the passageway 26.

Means is provided for pivotally mounting the paddle assembly 31 outsidethe fluid passageway 26 upper and lower pivot and jewel mountings 35 and36. The paddle assembly 31 is a part of removing and restoring systemwhich also includes a rectangular moving coil 37 that forms part of atorque motor 38 for applying a restoring force directly to the paddleassembly 31. The moving coil 37 is disposed in air gap 39 formed betweena magnet 41 and a U-shaped soft iron yoke 42, both of which are mountedon the base 18 by a suitable means such as cement. The upper pivot andjewel mounting 35 is carried by the yoke 42 as the lower pivot and jewelmounting 36 is carried by a block 43 formed integral with the base 18.Hair springs 46 are provided on each end of the moving coil and areprovided for supplying current to the moving coil. Thus, it can be seenthat the paddle assembly is supported about its pivot axis so that thereis substantially no constraint about its pivot axis in the absence of arestoring current supplied by the electronics module 16.

Means is provided for sensing the position of the paddle member 32 ofthe paddle assembly 31 and consists of a pick-off coil 48 which iscarried by a mounting block 49 mounted upon the base 18. The pick-offcoil 48 is connected to the electronics module 16 that is housed in acase 51 secured to the base plate 11 by a large screw 52 which extendsthrough the case 51, through the end portion 11b of the base plate 11and is threaded into the base 18. A plurality of terminals 53 aremounted upon the module 16 and have connected thereto a plurality ofleads 54. i

The bellows assembly 14 consists of a generally cylindrical base 56 anda generally cylindrical cover 57 which is secured to the base. The base56 is mounted upon the cover 19 of the electronics module 16 by suitablemeans such as a rivet 58. A beryllium copper bellows 61 is mounted inthe hole 62 provided in the cover 57 and is disposed in the space 63provided by the base 56 and the cover 57. The interior of the bellows 61is open to the atmosphere, whereas the space 63 within the base 56 andthe cover 57 is exposed to the oil pressure within the space 28 of thesensing assembly 12 through a grommet 66 which is mounted on the base 56and in the cover 19. The grommet 66 is provided with a flow passage 67that establishes communication between the space 63 and the space 28.The bellows assembly 14 which is provided is relatively large toaccommodate the relatively large volume of fluid which is utilized inthe accelerometer. 1

mounting purposes.

sembly 73 is connected to the electronics module 16 as shown in FIG. 6.The electronics module 16 includes acceleration electronics 74 whichproduces an electrical output signal E, that is proportional to theacceleration. The acceleration electronics 74 can be of a type disclosedin Morris US. Pat. No. 3,074,279 in which the pick-off coil 48 isconnected to an oscillator and in which the output of the oscillator isfed into a detector that has its output amplified by an output amplifier14. The output of the amplifier is fed through a load resistance andthrough a feedback path to the moving .coil 37 to cause the moving coilto supply a restoring force to the paddle assembly. The restoring forcewhich is supplied to the moving coil determines the magnitude ofacceleration being measured. The electronics provides a signal which isproportional to this rate of acceleration which is the signal E shown inFIG. 6.

This is supplied to an analog integrator 76 which also the angular ratesensor 10 has been placed in an environment in which it is to measurethe rate of turn about its sensitive axis, namely, and axis coincidentwith the axis of rotation of the fluid rotor which is formed by thefluid mass in the endless annular passageway 26. When the sensor issubjected to angular rotation about the sensitive axis, a positive errorsignal is generated by the accelerometer as the fluid rotor (due to itsinertia) tends to lag behind the accelerating case or base 11 of thesensor. The paddle member 33 disposed in the fluid path of the fluidrotor serves to constrain the fluid rotor to cause it to move with thecase of the accelerometer. As soon as the fluid rotor causes a slightmovement of the paddle member 33, the paddle member 32 will also bemoved and this movement will be sensed by the pick-off coil 48. Asexplained in Morris US. Pat. No. 3,074,279 since the pick-off coil isexcited by the oscillator electronics, the oscillator output ismodulated by the variation in spacing between the end paddle member 33and the pickofi coil. This is detected and changed to a high levelcurrent. The output amplifier brings the power level up to wheresuflicient current is applied to the moving coil to restore the paddleassembly to its zero or null position, preventing the fluid rotor fromshifting in position and causing the fluid rotor to move with the caseof the accelerometer. Thus, it can be seen that the power amplifierproduces a power level which is sufficient to retain the paddle assemblyin a zero or null position and the current which flows actuallyrepresents the ac- I ce'leration acting upon the fluid rotor. For thisreason,

All of the parts of the angular rate sensor thus far I as shown in FIG.6 which is adapted to receive the angular acceleration indicated as(0,103 The sensing asthe output current is not a function of anyresistance in the output circuit but is only a function of theacceleration which the accelerometer is undergoing.

The fluid rotor serves as the inertial mass in the accelerometer whichis closely coupled to an almost weightless, low inertial torque motoroperating in a closed loop fashion to sense the angular motion of thefluid rotor and to provide the torque necessary to constrain the rotorto move with the case of the accelerometer. Thus, the paddle assembly 31supplies the force necessary to accelerate the fluid mass so that itmoves with the case and prevents it from circulating.

The moving parts of the torque motor are symmetrical and are carefullybalanced in and out of the fluid to assure a minimum G sensitivity ofthe finished accelerometer. The use of the neutrally buoyant torquemotor rather than a neutrally buoyant mass reduces the balance problemsby several orders of magnitude in initial value and as well, makes the Gsensitivity of the unit almost independent of variation of fluid densitywith temperature.

Although the tubular assembly 13 is shown as lying in a plane, this isnot necessary as long as the sensitive axis of the device can bedetermined.

As explained previously, the electronic module serves to close the servoloop around the sensor and to provide an electrical output signal Eproportional to the angular acceleration. As shown in FIG. 6, thisangular acceleration is converted into a velocity signal by integratingit in the analog integrator 76. This analog integrator produces a signalwhich is proportional to the rate of turn of the sensor. To provide asubstantially constant output from the integrator, the relatively largeresistor R2 is placed across the analog integrating capacitor C whichshunts the capacitor C that causes a small leakage current to flow toprevent saturation. The use of the analog integrator produces anelectrical output signal E which is proportional to the rate of turn orvelocity of the sensor.

The angular accelerometer is incapable of going down to d.c. in therange of signal frequencies because the angular accelerometer does notintegrate. In such a case it merely amplifies the acceleration output ESuch results are shown in FIG. 7 which represents the frequency responseof a typical fluid rate sensor in the form of bode asymptotes showingthe band-pass characteristics of the fluid rate sensor with a flatresponse from 0.1 to Hertz to input rates. Below 0.] Hertz the output toa rate input would fall off at 6 lb. per octave. Above 20 Hertz, thenatural cut-off of the sensing assembly 12 is reached and therefore theoutput would fall off at 12 lb. per octave.

It can be seen that this rate sensor has an unusual characteristic whencompared with a conventional rate gyro. A rate gyro goes down to a d.c.output which will be steady with a steady input rate. In the ratesensor, the large resistor R2 eliminates the d.c. response. to the inputrate. However, the rate sensor will produce the proper rate signal assoon as the rate sensor is accelerated although that rate will decay tozero with a steady input rate.

Another embodiment of the invention is shown in FIGS. 8 and 9 which isvery similar to the embodiment which is shown in FIGS. 1-5 with theexception that the parts have been re-arranged so that the axis ofsensitivity has beenshifted by 90. Thus, a base plate 81 has beenprovided which is narrower and which is provided with two upturnedportions 81a and 81b. The sensing assembly 12 and the bellows assembly14 have been provided with flats and have been arranged so that they areside by side and interconnected in the same manner that the twoassemblies were interconnected in the previous embodiment. A tubularassembly 86 similar to the tubular assembly 13 has been provided andconsists of tube sections 87 and 88 interconnected by a coupling 89. Thetube sections 87 and 88 are mounted in the cover 19 of the sensingassembly 12 as shown in the cross-section in FIG. 9. As shown therein,the ends of the tubular sections 87 and 88 are joined together toprovide indented portions 87a and 880, respectively, so as to create aflow passage therebetween which is substantially perpendicular to theplane of the end member 32 of the paddle assembly 31. With thisarrangement it can be seen that the entire angular accelerometer takesless space and that the expansion or bellows assembly 14 and the sensingassembly 12 are both within the confines of the tubular assembly 13. Theoperation of this embodiment of the invention is identical to thatdescribed for the embodiment shown in FIGS. l-S. The paddle 32 againserves to constrain the fluid rotor disposed within the tubular assembly86 as the base plate 81 is subjected to angular rotation about thesensitive axis for the angular rate sensor.

In FIG. 10 there is shown a three-axis angular rate sensor 96. Itconsists of a framework 97 which has three substantially planar plates101, 102 and 103 Z planes. are fastened together to form X, Y and Thesensitive axis for each single axis angular accelerometer is at rightangles to the plate on which it is mounted. A single axis rate sensorofthe type hereinbefore described is mounted on each of the plates 101,102 and 103 to provide a three-axis or tri-axis rate sensor. Thisthree-axis angular rate sensor 96 which is shown in FIG. 10 can beutilized as a direct replacement'for a rate gyro system that is commonlyutilized on aircraft. There are many advantages in doing this. The ratesensor normally would cost substantially less than a conventional rategyro. It also would take much less space and would be much lighter. Inaddition, the reliability would be greatly increased and The maintenancerequired would be decreased very substantially.

Such a rate sensor is also advantageous in that it only requires a d.c.power output and provides a direct d.c. voltage output which isproportional to the angular acceleration or, with processing, theangular rate. Rate gyros, on the other hand, require an a.c. voltage forexcitation and thus the errors are related to the frequency stability ofthe a.c. excitation. The d.c. output from the rate sensor is desirablein that it can be processed by filtering means and otherwise shapedwithout having to demodulate it as would be necessary with the a.c.output of a rate gyro.

The rate sensor would be utilized for detecting dynamic rather thanstatic inputs as, for example, for detecting changing rates as would befound in yawing aircraft or pitching aircraft due to turbulence orerratically induced maneuvers. The output information which is obtainedcould be utilized in the auto pilot system which, in turn, would commandthe appropriate flight control surfaces of the aircraft to thereby causethe aircraft to fly smoothly and stably.

It is apparent from the foregoing that there has been provided a fluidrotor angular rate sensor utilizing the same which has many advantageousfeatures permitting its use in many applications. I

I We claim:

1. In an angular rate sensor for sensing angular rate about apredetermined axis, means forming a base plate, a sensing assemblymounted on the base plate, said sensing assembly including means mountedon the base plate forming a substantially continuous passageway, a fluiddisposed in said passageway, a paddle assembly mounted upon the baseplate for pivotal movement and having a portion thereof disposed in thepassageway and serving to inhibit the flow of fluid in the passageway,electrical means for retaining the paddle assembly in a predeterminedposition with respect to the base plate and providing an electricaloutput signal which determines the force which is necessary toaccelerate the fluid in the fluid passageway as the base plate isaccelerated about an axis, and additional electrical means forintegrating the electrical output signal to provide an additionalelectrical output signal which is proportional to the rate of turn ofthe sensor, said additional electrical means including means to preventthe generation of a gradually increasing additional electrical outputsignal which could cause saturation, said additional electrical outputsignal having a band pass for a predetermined frequency range with upperand lower corner frequencies, the upper corner frequency beingdetermined by the natural cut-off of the sensing assembly and said firstnamed electrical means, said lower corner frequency being determined bythe additional electrical means, said additional electrical outputsignal being nominally zero for a substantially constant input rateabout said axis.

2. A sensor as in claim 1 wherein said electrical means for integratingthe first named electrical output signal includes an operationalamplifier, a capacitor connected between the output of the operationalamplifier and the input of the operational amplifier and a resistorconnected in parallel with the capacitor.

3. In an angular rate sensor, means forming a base, a sensing assemblymounted on the base plate, said sensing assembly including means mountedon the base forming a substantially continuous passageway about asensitive axis, a fluid mass disposed in the passageway and forming afluid rotor, a paddle assembly, means pivotally mounting the paddleassembly outside of the passageway about a pivot axis, the paddleassembly having a member disposed in said passageway in a direction atsubstantially right angles to the normal path of movement of the fluidmass in the passageway at the point where the fluid mass comes intocontact with the member of the paddle assembly, means for sensing theposition of the member in the passageway, said fluid mass serving toapply a force to the member of the paddle assembly when the base of theangular accelerometer is subjected to acceleration about the sen--sitive axis of the sensor, electrical means connected to the means forsensing the position of the planar member for applying a restoring forcedirectly to the paddle assembly which is proportional to the forceapplied to the member by the fluid mass as the base is subjected toangular acceleration about the sensitive axis to constrain movement ofthe fluid mass in said passageway, said paddle assembly being supportedabout its pivot axis so that there is substantially no constraint aboutits pivot axis in the absence of the restoring force supplied by theelectrical means, said electrical means providing an electrical outputsignal proportional to the acceleration measured, and additionalelectrical means for integrating the electrical output signal to providean additional electrical output signal which is proportional to the rateof turn of the sensor, said additional electrical means including meansto prevent the generation of a gradually increasing additionalelectrical output signal which could cause saturation, said additionalelectrical output signal having a band pass for a predeterminedfrequency range with upper and lower comer frequencies, the upper cornerfrequency being determined by the natural cut-off of the sensingassembly and said first named electrical means, said lower comerfrequency being determined by the additional electrical means, saidadditional electrical output signal being nominally zero for asubstantially constant input rate about said axis.

4. A sensor as in claim 3 wherein said means for integrating the firstnamed electrical output signal includes an operational amplifier, acapacitor connected between the output of the operational amplifier andthe input of the operational amplifier and a resistor connected inparallel with the capacitor.

5. In a three-axis angular rate sensor, means forming a framework,first, second and third single-axis angular rate sensors, means mountingsaid first, second and third single-axis angular rate sensors on saidframework so that said single axis angular rate sensors have theirsensitive axes disposed on X, Y and Z axes, respectively, each of saidsingle'axis angular rate sensors including means forming a base, meansmounted on the base forming a substantially continuous passageway, afluid mass disposed in the passageway and forming a fluid rotor, apaddle assembly mounted upon the base plate for pivotal movement andhaving a substantially planar member forming a part thereof and disposedinthe fluid passage and serving to constrain movement of the fluid massin the passageway, means for sensing the position of the member in thepassageway, said fluid mass serving to apply a force to the member ofthe paddle assembly when the base is subjected to angular accelerationabout the sensitive axis, electrical means connected to the means forsensing the position of the paddle member for applying a restoring forcedirectly to the paddle member which is proportional to the force appliedto the paddle member by the fluid mass as the base is subjected toangular acceleration to constrain movement of the fluid mass in thepassageway, said electrical means including means for providing a signalwhich is proportional to the rate of angular acceleration and additionalelectrical means for integrating the signal to provide an electricaloutput signal which is proportional to the rate of turn, said additionalelectrical means including means to prevent the generation of agradually increasing electrical output signal which could causesaturation, said additional electrical output signal having a band passfor a predetermined frequency range with upper and lower cornerfrequencies, the upper corner frequency being determined by the naturalcut-off of the sensing as sembly and said first named electrical means,said lower comer frequency being determined by the additional electricalmeans, said additional electrical output signal being nominally zero fora substantially constant input rate about said axis.

" InAn

1. In an angular rate sensor for sensing angular rate about apredetermined axis, means forming a base plate, a sensing assemblymounted on the base plate, said sensing assembly including means mountedon the base plate forming a substantially continuous passageway, a fluiddisposed in said passageway, a paddle assembly mounted upon the baseplate for pivotal movement and having a portion thereof disposed in thepassageway and serving to inhibit the flow of fluid in the passageway,electrical means for retaining the paddle assembly in a predeterminedposition with respect to the base plate and providing an electricaloutput signal which determines the force which is necessary toaccelerate the fluid in the fluid passageway as the base plate isaccelerated about an axis, and additional electrical means forintegrating the electrical output signal to provide an additionalelectrical output signal which is proportional to the rate of turn ofthe sensor, said additional electrical means including means to preventthe generation of a gradually increasing additional electrical outputsignal which could cause saturation, said additional electrical outputsignal having a band pass for a predetermined frequency range with upperand lower corner frequencies, the upper corner frequency beingdetermined by the natural cut-off of the sensing assembly and said firstnamed electrical means, said lower corner frequency being determined bythe additional electrical means, said additional electrical outputsignal being nominally zero for a substantially constant input rateabout said axis.
 2. A sensor as in claim 1 wherein said electrical meansfor integrating the first named electrical output signal includes anoperational amplifier, a capacitor connected between the output of theoperational amplifier and the input of the operational amplifier and aresistor connected in parallel with the capacitor.
 3. In an angular ratesensor, means forming a base, a sensing assembly mounted on the baseplate, said sensing assembly including means mounted on the base forminga substantially continuous passageway about a sensitive axis, a fluidmass disposed in the passageway and forming a fluid rotor, a paddleassembly, means pivotally mounting the paddle assembly outside of thepassageway about a pivot axis, the paddle assembly having a memberdisposed in said passageway in a direction at substantially right anglesto the normal path of movement of the fluid mass in the passageway atthe point where the fluid mass comes into contact with the member of thepaddle assembly, means for sensing the position of the member in thepassageway, said fluid mass serving to apply a force to the member ofthe paddle assembly when the base of the angular accelerometer issubjected to acceleration about the sensitive axis of the sensor,electrical means connected to the means for sensing the position of theplanar member for applying a restoring force directly to the paddleassembly which is proportional to the force applied to the member by thefluid mass as the base is subjected to angular acceleration about thesensitive axis to constrain movement of the fluid mass in saidpassageway, said paddle assembly being supported about its pivot axis sothat there is substantially no constraint about its pivot axis in theabsence of the restoring force supplied by the electrical means, saidelectrical means providing an electrical output signal proportional tothe acceleration measured, and additional electrical means forintegrating the electrical output signal to provide an additionalelectrical output signal which is proportional to the rate of turn ofthe sensor, said additional electrical means including means to preventthe generation of a gradually increasing additional electrical outputsignal which could cause saturation, said additional electrical outputsignal having a band pass for a predetermined frequency range with upperand lower corner frequencies, the upper corner frequency beingdetermined by the natural cut-off of the sensing assembly and said firstnamed electrical means, said lower corner frequency being determined bythe additional electrical means, said additional electrical outputsignal being nominally zero for a substantially constant input rateabout said axis.
 4. A sensor as in claim 3 wherein said means forintegrating the first named electrical output signal includes anoperational amplifier, a capacitor connected between the output of theoperational amplifier and the input of the operational amplifier and aresistor connected in parallel with the capacitor.
 5. In a three-axisangular rate sensor, means forming a framework, first, second and thirdsingle-axis angular rate sensors, means mounting said first, second andthird single-axis angular rate sensors on said framework so that saidsingle axis angular rate sensors have their sensitive axes disposed onX, Y and Z axes, respectively, each of said single axis angular ratesensors including means forming a base, means mounted on the baseforming a substantially continuous passageway, a fluid mass disposed inthe passageway and forming a fluid rotor, a paddle assembly mounted uponthe base plate for pivotal movement and having a substantially planarmember forming a part thereof and disposed in the fluid passage andserving to constrain movement of the fluid mass in the passageway, meansfor sensing the position of the member in the passageway, said fluidmass serving to apply a force to the member of the paddle assembly whenthe base is subjected to angular acceleration about the sensitive axis,electrical means connected to the means for sensing the position of thepaddle member for applying a restoring force directly to the paddlemember which is proportional to the force applied to the paddle memberby the fluid mass as the base is subjected to angular acceleration toconstrain movement of the fluid mass in the passageway, said electricalmeans including means for providing a signal which is proportional tothe rate of angular acceleration and additional electrical meaNs forintegrating the signal to provide an electrical output signal which isproportional to the rate of turn, said additional electrical meansincluding means to prevent the generation of a gradually increasingelectrical output signal which could cause saturation, said additionalelectrical output signal having a band pass for a predeterminedfrequency range with upper and lower corner frequencies, the uppercorner frequency being determined by the natural cut-off of the sensingassembly and said first named electrical means, said lower cornerfrequency being determined by the additional electrical means, saidadditional electrical output signal being nominally zero for asubstantially constant input rate about said axis.